Generally, when a driver shot or iron shot is made in golf, a posture of a player and a hitting point on a golf ball are important for securing a desired driving distance and direction of the golf ball. Particularly, the golf ball can travel a large distance only by hitting a portion of a golf ball spaced a predetermined distance from the center of the golf ball downward such that the golf ball rotates backward and a lift force occurs in a direction perpendicular to a travel direction of the golf ball. When this principle is particularly applied to golf, in order to send a golf ball flying far away in a desired direction, accurately checking the center of gravity of the golf ball to hit the golf ball is recognized as being important to players.
Here, the golf ball to be used in golf games is manufactured with a diameter greater than 1.68 inches (42.67 mm) and a weight less than 1.62 ounces (45.93 g). As shown in FIG. 1, generally, the golf ball includes a core (2) formed at the center and a cover (3) which surrounds the core (2).
However, since mass-produced golf balls have centers of gravity different from each other and may also have weights different from each other, it is very difficult to find the center of gravity of each golf ball and to set an upper point of the center of gravity as an axis of rotation.
That is, since a core of a golf ball is heavier than a cover thereof, when the core is not positioned at the center of the golf ball and is biased to one side, a heavy side and a light side are generated in the golf ball necessarily causing the golf ball to be unbalanced, and thus, a trajectory of the golf ball has to bend in a direction of the heavy side because a weight distribution of left and right sides is non-uniform when the golf ball spins.
Accordingly, recently, a golf ball is used with a putting line arbitrarily marked on an outer circumferential surface thereof. However, the putting line causes a problem in that the golf ball is hit inaccurately due to the low accuracy of the line.